With summer coming, people are turning on air conditioning in most parts of the United States, but if you are like me, you always feel introverted about it. The past few generations have not had air conditioning – do I really need it? How bad is it to use all this electricity for cooling in a warm world?
If I put the air conditioner down, I would be too hot. But if everyone turns on their air conditioners at the same time, electricity demand spikes, which could force grid operators to activate some of the most expensive and dirtiest power plants. Sometimes these spikes can ask too much of the grid and cause Blunt or power outages.
My recent research published with a group of scholars made me feel better. We found that the operation of a large number of home air conditioning units can be coordinated to balance supply and demand on the grid without putting people in their homes.
Research along these lines, such theoretical possibilities have been explored over the years using remote controls that support the grid. However, in practice, there are few people who demonstrate the method and have never been such high-value applications and this scale. The system we developed not only demonstrates the ability to balance grids on a time scale of seconds, but also demonstrates that it can be done without affecting residents’ comfort.
Benefits include increased reliability of the grid, which makes the grid more receptive to more renewable energy. Our goal is to transform air conditioners from challenges to the grid into assets and support the shift from fossil fuels to clean energy.
Adjustable equipment
My research focuses on batteries, solar panels and electric equipment such as electric cars, water heaters, air conditioners and heat pumps – they can be adjusted at different times to consume different amounts of energy.
Initially, the U.S. power grid was designed to transport electricity from large power plants to customers’ homes and businesses. Initially, power plants were large centralized operations, burning coal or natural gas, or harvesting energy from nuclear reactions. These plants are often always available and can adjust the power generated by their response to customer needs, so the grid will balance between producer power and consumer use.
But the grid has changed. There are more renewable energy sources that don’t always get power from them – like solar panels at night or calm days. The equipment and equipment I research. These updated options, called “distributed energy”, generate or store energy where consumers need it, or adjust the energy used in real time.
However, one aspect of the grid has not changed: the system has not built-in storage space. So, every time the light is turned on, there is not enough power to provide everything you want it: the grid needs a power producer to generate more power. And, when you turn off the lights, there is so much: a power producer needs to gradually lower it.
The power plant knows what real-time power supply adjustments are needed to closely monitor grid frequency. The goal is to always provide power at a constant frequency (60 Hz). If more power is needed than more power is generated, the frequency drops and the power plant increases the output. If too much power is generated, the frequency will rise and the power plant will slow down production slightly. These actions are a process called “frequency adjustment” that takes place within seconds to maintain balance.
This output flexibility comes primarily from the power plant and is key to keeping the lights for everyone.
Find new options
I’m interested in how distributed energy can improve the flexibility of the power grid. They can release more energy or reduce consumption to cope with changing supply or demand and help balance the grid to ensure frequency remains around 60 Hz.
Some people worry that doing so can be invasive, allowing someone outside your home to control the battery or air conditioner. So we wanted to see if we could use a home air conditioning unit instead of a power plant to help balance the grid with frequency adjustment without affecting how residents use their own equipment or the comfort of their home.
From 2019 to 2023, my team at the University of Michigan worked with researchers at Pecan Street Inc., Los Alamos National Laboratory and the University of California, Berkeley, and received funding from the U.S. Energy Advanced Research Projects Agency-Energy.
We recruited 100 homeowners in Austin, Texas to test our system in reality. All homes have full-room forced air cooling systems that we connected to a custom control panel and sensors that the owner allowed us to install in our home. This device lets us send instructions to the air conditioning unit according to the frequency of the grid.
Before explaining how the system works, I first need to explain how the thermostat works. When people set up a thermostat, they choose a temperature that switches and turns off the air conditioner compressor to keep the temperature within a smaller range near that set point. If the temperature is set to 68 degrees, the thermostat turns on AC at 70 and turns it off to 66 when it cools.
Every few seconds, our system slightly changes the timing of some of the air conditioner compressors in the 100 air conditioners, resulting in a change in the total power consumption of the unit. In this way, our small group of home air conditioners on the grid will change like a power plant – using more or less energy to balance the grid and keep the frequency around 60 Hz.
Additionally, our system is designed to keep home temperatures within the same temperature range near the set point.
Test Method
We ran the system in four tests, each lasting an hour. We found two encouraging results.
First, air conditioners can provide frequency adjustments at least as accurately as traditional power plants. Therefore, we show that air conditioners can play an important role in improving grid flexibility. But perhaps more importantly – at least in encouraging people to engage in such systems – we found that we were able to do so without affecting people’s comfort at home.
We found that the deviation between the home temperature and the set point does not exceed 1.6. If the homeowner is uncomfortable, the homeowner is allowed to cover the controls, but most people don’t. For most tests, we receive zero coverage requests. In the worst case, we received two of the 100 homes in our tests.
In fact, this technology can be added to the thermostat connected to the internet. In exchange for credits on their energy bills, users can choose to join services operated by thermostat companies, utility providers or other third parties.
People can then turn on the air conditioner in the summer heat without that guilt because they know they are helping to make the grid more reliable and capable of containing renewable energy – without sacrificing their comfort in the process.
Johanna Mathieu, associate professor of electrical engineering and computer science at the University of Michigan. This article is republished from the conversation under the Creative Sharing License. Read the original article.
